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  <script>
    // 1 号是周一， 以此类推， 23号

    // 1   1
    // 2   2
    // 3   3
    // 4  4
    // 5  5
    // 6  6
    // 7  日

    // 8  1
    // 9 2
    // 10 3
    // 85980366
    var num = parseInt( prompt('输入日期') )

    switch( num % 7 ) {
      case 1: 
        console.log('周一')
        break
      case 2: 
        console.log('周2')
        break
      case 3: 
        console.log('周3')
        break
      case 4: 
        console.log('周4')
        break
      case 5: 
        console.log('周5')
        break
      case 6: 
        console.log('周6')
        break
      default:
        console.log('周日')
    }





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